Capsaicin is a chemical isolated from the fruits of plants of the nightshade family, principally the pepper plant. It requires processing of about 10,000 pounds of peppers to extract a yield of 1 pound of capsaicin. Capsaicin has in recent years been used topically on the skin to treat psoriasis and to relieve certain types of superficial pain.
Ground pepper, containing capsaicin, has long been utilized by magicians and tricksters as "sneezing powder". It affects the nose and airway passages of the respitory system by causing intense irritation, producing vigorous sneezing and coughing and, if exposure is extreme, shortness of breath. Additionally, direct exposure of pepper to the mucosa of the nose may result in intense local pain, and not uncommonly, severe headache.
It has been discovered that capsaicin, when applied repeatedly locally to the nasal mucosa or directed to the respiratory passages can produce quite contrary and surprising effects.
In particular, it has been found that capsaicin has beneficial effects in treating the symptoms of vasomotor rhinitis, commonly encountered throughout the year, and allergic rhinitis encountered during the ragweed and mold season. It was noticed that a person suffering from these conditions, while working with capsaicin powder, inhaled relatively large amounts of the powder over a several day period, causing intense burning pain and sneezing. This was followed several hours later by an intense headache involving the tempero-frontal areas. On the second day of exposure to the powder, the foregoing symptoms were similar, but less intense. After four days of exposure, the subject no longer experienced the intense nasal pain, sneezing, or headache, but noticed that congestion from vasomotor rhinitis was no longer apparent. Indeed for the next few days, the subject experienced substantially less of his usual seasonal nasal discomfort.
On the basis of these results, solutions of capsaicin were prepared for introduction into the nose to treat allergic and other inflammatory disorders of the nose as well as to prevent or treat headaches. In introducing such drops into the nasal passages of several test subjects it was discovered that the capsaicin drops could produce intense almost unbearable pain in the naive patient. Several types of other agents were then incorporated into the formulation along with the capsaicin to relieve this adverse reaction to the capsaicin nose drops. In the course of trying to reduce this adverse capsaicin effect, the topical anesthetics lidocaine (Entry 5310, p. 786, Merck Index, Tenth Edition 1983,and benzocaine (ethyl aminobenzoate, Entry 3710, p. 546, Merck Index, Tenth Edition 1983, the topical steroids hydrocortisone and betamethasone valerate and the histamine blockers diphenhydramine, doxepin and amitriptyline were used.
It was discovered that the topical anesthetics lidocaine and benzocaine, in concentrations of from about 0.5% to about 20% were most effective in preventing the intense burning pain of the nasal mucosa induced by capsaicin. Topical steriods and anihistamines appeared to reduce the burning effects of capsaicin, but to a lesser degree than the anesthetics.